A Quantitative Approach to Identify Morphological Features Relevant for Visual Function in Ranibizumab Therapy of Neovascular AMD

Purpose: To quantitatively analyze morphological features in eyes with neovascular AMD (nAMD) at baseline, after 12 months, and after 24 months of intravitreal ranibizumab treatment and to perform a structure/function correlation.

Methods: Eyes with treatment-naïve nAMD were treated with intravitreal ranibizumab according to a standardized dosing regimen over 2 years and followed continuously in a prospective study design. The central foveal area of 1000 μm (horizontal)×960 μm (vertical) of spectral-domain optical coherence tomography (SD-OCT) volume scans was evaluated quantitatively (using proprietary software) for the following pathologies: alteration of the external limiting membrane (ELM), alteration of the ellipsoid zone, subretinal fluid, pigment epithelium detachment, drusen, intraretinal cysts, subretinal mass, and subretinal pigment epithelium mass. The total area of each pathology was calculated in mm2 at baseline and after 1 and 2 years of ranibizumab therapy and correlated with BCVA results.

Results: In total, 480 central SD-OCT scans of 20 consecutive patients were evaluated. In the multivariate regression analysis, the area of ELM alteration, the area of intraretinal cysts, and foveal retinal thickness were significant variables influencing visual acuity at baseline (R=-0.827; R2=0.684; P<0.001). The area of ELM alteration was the only significant factor to be directly associated with visual acuity at 12 months (R=-0.846; R2=0.716; P<0.001) and 24 months (R=-0.778; R2=0.606; P<0.001).

Conclusions: The integrity of the ELM appears to be the most important feature correlating with visual acuity in native nAMD as well as nAMD treated with intravitreal ranibizumab at each time interval, but not prospectively. In general, no significant predictors for an individual gain or loss in mid- (12 months) or long-term BCVA results (24 months) were found by OCT.